1. Field of the Invention
The present invention relates to methods, apparatus and articles used for the analysis of data. More particularly, it relates to methods, apparatus and articles used to reduce large amounts of data to much smaller forms. More particularly still, it relates to methods, apparatus and articles which may be used to reduce the data to a form conducive to efficient analysis of the data.
2. Prior Art
There are many instances in which a great deal of data is produced, and it is a lengthy and costly process to analyze the data. By way of example only, and not by way of limitation, in the broadcast industry, it is desirable to monitor the programs broadcast by stations to determine whether specific content, such as for example music or songs, have been broadcast.
An example of how this may be accomplished is disclosed in U.S. Pat. No. 5,437,050, entitled Method and Apparatus for Recognizing Broadcast Information Using Multi-Frequency Magnitude Detection, issued to Lamb et a1. and assigned to the same assignee as that of the present invention.
As noted in this patent, a wide variety of copyrighted recordings and commercial messages are transmitted by broadcast stations. Copyrighted works such as moving pictures, television programs, and phonographic recordings attract audiences for broadcast stations, and the aforementioned commercial messages, when sent to the audiences, provide revenue for the broadcast stations.
There is an interest among various unions, guilds, performance rights societies, copyright owners, and advertising communities in knowing the type and frequency of information being broadcast. Owners of copyrighted works, for example, may be paid a royalty rate by broadcast stations depending on how often their copyrighted work is broadcast. Similarly, commercial message owners such as advertisers, who pay broadcast stations for air time, have an interest in knowing how often their commercial messages are broadcast.
It is known in the art that commercial radio and television broadcast stations are regularly monitored to determine the number of times certain information is broadcast. Various monitoring systems have been proposed in the prior art. In manual systems, which entail either real-time listening or delayed listening via video or audio tapes, people are hired to listen to broadcast information and report on the information they hear. Manual systems although simple, are expensive, lack reliability, and are very often highly inaccurate.
Electronic monitoring methodologies offer advantages over manual systems such as lower operating costs and reliability. One type of electronic monitoring methodology requires insertion of specific codes into broadcast information before the information is transmitted. The electronic monitoring system can then recognize a song, for example, by matching the received code with a code in a reference library. Such systems suffer from both technical and legal difficulties. For example, such a coding technique requires circuitry, which is expensive to design and assemble and which must be placed at each transmitting and receiving station. Legal difficulties stem from the adverse position of government regulatory agencies toward the alteration of broadcast signals without widespread acceptance thereof by those in the broadcast industry.
A second type of electronic monitoring methodology requires pre-specification of broadcast information into a reference library of the electronic monitoring system before the information can be recognized. A variety of pre-specification methodologies have been proposed in the prior art. The methodologies vary in speed, complexity, and accuracy. Methodologies which provide accuracy are likely to be slow and complex, and methodologies which provide speed are likely to be inaccurate.
The apparatus and method described in the above mentioned U.S. Pat. No. 5,437,050 has met with commercial success and has in large part met the needs of many segments of the broadcast industry. This approach is based on the discovery that the broadcast information on which recognition is based lies in the narrow frequency bands associated with the semitones of the music scale, rather than in the continuum of audio frequencies or in other sets of discrete frequency bands. It is also based on the principle that the set of semitones that have energies above a threshold amount at each instance provide sufficient information for recognition, and that it is not necessary to use the absolute energies of all frequencies for recognition.
Thus, U.S. Pat. No. 5,437,050 provides an apparatus and a method of recognizing broadcast information, including the steps of receiving broadcast information, the broadcast information being in analog form and varying with time; converting the broadcast information into a frequency representation of the broadcast information; dividing the frequency representation into a plurality of separate frequency bands (generally 48 bands over four octaves); determining a magnitude of each separate frequency band of the digital sample; and storing the magnitudes. The method of recognizing broadcast information also includes the steps of performing a significance determination a plurality of times, the significance determination including the steps of generating a magnitude of each separate frequency band, using a predetermined number of previously stored magnitudes for each respective frequency band; storing the magnitudes; and determining a significance value, using a predetermined number of previously stored magnitudes for each respective frequency band. The method of recognizing broadcast information further includes the steps of comparing the significance value to the most recently generated magnitude of each separate frequency bands generating a data array, the data array having a number of elements equal to the number of separate frequency bands, the values of the elements being either binary 1 or binary 0 depending on the results of the comparison; reading a reference data array, the reference data array having been generated from reference information; comparing the data array to the reference data array; and determining, based on the comparison, whether the broadcast information is the same as the reference information.
U.S. Pat. No. 5,437,050 also provides a digital recording method in conjunction with the monitoring system to achieve recognition of broadcast information pre-specified to the monitoring system. The digital recording method can also achieve recognition of broadcast information not previously known to the monitoring system, while preserving a complete record of the entire broadcast period which can be used for further reconciliation and verification of the broadcast information.
More specifically, the method of recording broadcast information, includes the steps of receiving a set of broadcast information; recording the set of broadcast information in a compressed, digital form; generating a representation of the set of broadcast information; comparing the representation to a file of representations; making a determination, based on the comparison, of whether the representation corresponds to any representations in the file; upon a determination that the representation corresponds to a representation in the file, recording the broadcast time, duration, and identification of the set of broadcast information that corresponds to the representation; upon a determination that the representation does not correspond to any representations in the file, performing the following steps: (a) performing a screening operation on the representation in order to discern whether the representation should be discarded; (b) upon a determination that the representation should not be discarded, performing the following steps: (c) playing the recorded set of broadcast information which corresponds to the set of broadcast information from which the representation was generated in the presence of a human operator; and (d) making a determination, based on the playing of the recorded set of broadcast information, of whether the representation should be added to the file of representations and whether a recording should be made of the broadcast time, duration, and identification of the set of broadcast information that corresponds to the representation.
As noted above, while the technology described in U.S. Pat. No. 5,437,050 has been widely used, over the years it has become apparent that it has some limitations. While working well in its intended application, attempts to apply it to other applications have met with varying degrees of success. The technology is not extremely effective at short-term matching; that is determining whether a match exists between the data produced by a short segment of source material and a previously stored reference. In general, relatively few bits are set; on average, only 3 bits in a 48 bit frame. Often, the same bits are set for many frames in a row. When a strong melody is not present, continuity may be weak. Further, in the presence of a strong melody, it is possible that only one bit will be set for many frames.
Slightly different results may be produced, in terms of the specific bits set for the same source material, when different amounts of audio compression are used. Further, different bits may be set when transients are suppressed.